Some time ago in a post entitled "Breath Fresheners and Breathalyzers" I commented that one of many problems with breathalyzers was that they cannot distinguish alcohol coming from the blood by way of the lungs from alcohol in the mouth or throat. As a result, any use of breath fresheners or mouthwash will cause falsely high readings on the machines:

One common source of breath alcohol is breath spray, as well as mouthwash — both of which contain significant amounts of alcohol. Listerine, for example, contains 27% alcohol, Scope 19% and Astring-O-Sol 76%. Even a tiny amount of this on the breath or in the throat, if multiplied by the machine 2100 times, can result in high breathalyzer readings.

I failed to consider the possibility of a Listerine cocktail. For those doubting the strength of mouthwash, consider the following story from CNN:

ADRIAN, Michigan (AP) — A woman arrested after failing a sobriety test and telling police she drank three glasses of Listerine has pleaded guilty to drunken driving. Carol Ries, 50, was pulled over after she rear-ended another vehicle at a red light on January 9. She passed one breathalyzer test, but failed another that used different equipment. Police found a bottle of Listerine in her car, and she told them she had drunk three glasses earlier in the day. Her blood alcohol level was more than three times the legal limit, police said. According to Listerine manufacturer Pfizer Inc.'s Web site, original formula Listerine contains 26.9 percent alcohol, while other varieties contain 21.6 percent alcohol.

The focus of the story is on the novelty of drinking Listerine. But note that Ms. Ries "passed one breathalyzer test, but failed another". The first breathalyzer indicated a blood-alcohol concentration below the legal limit of .08%, while the second indicated a BAC of .30% — over three times the legal limit. Do you still believe these machines are accurate? If so, which one — if either? See my earlier posts, such as "Breathalyzers — and Why They Don't Work" and "Why Breathalyzers Don't Measure Alcohol".

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